It is becoming increasingly common for pay television systems to be utilized for the transmission of television programming to subscribers who are willing to pay either on a fixed periodic or pay per view basis for the programming. The most common pay television systems presently in use are operated in conjunction with cable system broadcast of television programming, but over-the-air systems also exist. The impetus behind the trend toward pay television broadcast is the need to generate monetary remuneration to program providers more than is normally obtainable through advertiser supported television or to program providers of programs for which the audience is more limited in size. In any pay television broadcast system, however, security needs to be a primary concern in order to ensure that viewers will pay for the programming broadcast rather than being able to gain unauthorized access to the broadcast programming in some fashion without the necessity for paying for the service.
Many systems are currently in operation for pay broadcast television, whether in cable or over the air, which include electronic scrambling of the broadcast television signal. Such a system requires a descrambler associated with the television receiving station and the descrambler must be, of course, particularly adapted to descrambling the type of scrambling imposed by the broadcast station on the particular broadcast signal. Usually a particular fixed format of decoder or descrambler is used at each receiving station which will in some fashion modify the broadcast signal in a way exactly complimentary to the way the scrambling device imposed a scrambling signal on the program signal at the broadcast station, so that the viewer views the complete unscrambled program at his location. The viewer is charged what is, in effect, a rental charge for use of the descrambler and usually this charge is made on a fixed periodic basis, i.e. monthly, regardless of how much programming is watched. One aspect of such systems is that it is possible for unauthorized or "pirate" descramblers to be constructed by persons knowledgeable in electronic design and these unauthorized descramblers can become available legally or illegally to those willing to pay for them. Once a potential viewer has legally or illegally purchased such a descrambler, he then has free and unimpeded access to the scrambled broadcast signals indefinitely.
One system which has been utilized to try and avoid the possibility of unauthorized scramblers being obtained and used indefinitely makes use of a numerical code which is operated on by an algorithm to predictably derive either a scrambling or descrambling signal. The broadcast station imposes one polarity of the signal produced by the algorithm as a scrambling signal on the program signal while the receiving station imposes the exact complementary signal using the same algorithm on the scrambled broadcast signal to descramble the program signal. In such a system it is necessary for the user to find out the code for the particular broadcast since the numerical code must be changed for each broadcast if unauthorized viewing is to be prevented for that broadcast. In the current systems in use, the viewer telephones the central billing station and requests the proper code for the particular broadcast he wishes to watch. The central station gets the identity of the viewer from his telephone call and gives the user the proper code which the user then enters onto a digital entry device contained on the decoding box at his viewing station to properly descramble the broadcast signal. The central station can then bill the viewer based on what programs the viewer has selected the proper code for. Such a system suffers from an obvious deficiency in that once the user knows the code, he can freely transmit that code to other subscribers to the system who have not given their names to the central billing station and the other subscribers may also then use that code to properly descramble and view the broadcast signal without paying for the service. Such a system may also occasionally have problems of access to the central billing facility during peak times when many viewers may call to request access to the proper codes to view particularly popular programs.
The more common systems in actual use today involve so-called "addressable" converters. These converters are descramblers located at the viewers station which can be selectively turned on or off by the broadcast station. They are called "addressable" since each descrambler has a unique address or identification which can be called by the broadcast station in turning the converter on or off.
Another aspect into which effort has been directed in developing pay television systems is in the method of billing to the subscriber of the system. Many current cable and premium cable channel systems are charged to their subscribers on a fixed monthly basis. It is believed by many in the industry that many additional viewers would subscribe to such systems if they were charged on a pay per view basis rather than on a monthly basis. Unfortunately, few cable or other pay broadcast systems are currently technically able to bill subscribers on a pay per view basis because of either the technical difficulty or practical inconvenience in monitoring actual program viewing.
Some systems have been developed and are described in the prior art which are capable of billing pay television subscribers on a pay per view basis. Most of these prior art systems are based on a telephone data linkage between the decoder at the subscribers station and a central billing facility. The decoder is dialed up, or selectively accessed in some other way, by the central billing facility on a periodic, i.e., daily or weekIy, basis to cause the decoder to transmit prerecorded viewing log information to the central facility. Such systems are obviously dependent upon a te-ephone linkage for their competent functioning. Other systems have been attempted in which some recording device is used at the receiving station which is sent to a billing facility to bill the viewer on a pay per view basis. These systems have not, however, had effective means to disable the viewers access to the programming if the viewer has not properly and timely paid his bill.
One system has been described, in U.S. Pat. No. 4,081,832, to Sherman, which makes use of a punched card carrying descrambling information thereon and which is also punched by the decoder to record program viewing.
No prior art television broadcast signal scrambling system is presently in actual use which cannot be overcome by a fixed electronic descrambler, if an unauthorized subscriber is willing to spend sufficient time and effort to develop or obtain such a descrambler in some unauthorized fashion. The present system is intended to provide such a system.